Balloon trocar

ABSTRACT

A balloon trocar includes a cannula assembly including a cannula and an outer sleeve fitting over the cannula. The distal end of the outer sleeve is proximal to the distal end of the cannula. A balloon is coupled to a distal portion of the sleeve and a distal portion of the cannula. The outer surface of the cannula includes a plurality of longitudinal channels for transmitting gas or fluid to the balloon. A bolster having a gel pad at its distal portion is slidably mounted to the cannula assembly and may be locked in a desired position. In use, the trocar is inserted into an incision through a body wall and into a body cavity. The balloon is inflated and the cannula assembly pulled proximally against the incision while the bolster is slid distally to the body wall and locked in place to seal the incision with the compressed balloon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/374,188, filed on Mar. 13, 2006, the disclosure of which ishereby incorporated by reference as if set forth in full herein. Thisapplication also claims the benefit of U.S. Provisional PatentApplication No. 60/744,819, filed on Apr. 13, 2006, U.S. ProvisionalPatent Application No. 60/820,579, filed on Jul. 27, 2006, U.S.Provisional Patent Application No. 60/892,925, filed on Mar. 5, 2007,and U.S. Provisional Patent Application No. 60/892,935, filed on Mar. 5,2007, the disclosures of which are hereby incorporated by reference asif set forth in full herein.

BACKGROUND

This invention relates generally to trocar systems including cannulasand, more specifically, to trocars having a balloon retention device.

Trocar systems have been of particular advantage in facilitating lessinvasive surgery across a body wall and within a body cavity. This isparticularly true in abdominal surgery where trocars have provided aworking channel across the abdominal wall to facilitate the use ofinstruments within the abdominal cavity.

Trocar systems typically include a cannula, which provides the workingchannel, and an obturator that is used to place the cannula across abody wall, such as the abdominal wall. The obturator is inserted intothe working channel of the cannula and pushed through the body wall witha penetration force of sufficient magnitude to result in penetration ofthe body wall. Alternatively, the cannula with an obturator is passedthrough an incision formed by the “Hassan,” or cut-down, technique,which includes incremental incisions through the body wall until thebody wall is incised through its entire thickness. Once the cannula hastraversed the body wall, the obturator can be removed.

With the cannula in place in the body wall, various instruments may beinserted through the cannula into the body cavity. One or more cannulasmay be used during a procedure. During the procedure, the surgeonmanipulates the instruments in the cannulas, sometimes using more thanone instrument at a time. The manipulation of an instrument by a surgeonmay cause frictional forces between the instrument and the cannula inwhich the instrument is inserted. These frictional forces may result inmovement of the cannula in an inward or outward direction within thebody wall. If the cannula is not fixed in place, the proximal or distalmotions of the instruments through the cannula may potentially cause thecannula to slip out of the body wall or to protrude further into thebody cavity, possibly resulting in injury to the patient.

The surfaces of the cannula associated with a trocar are generallysmooth. The smoothness of a cannula surface makes placement of thecannula through a body wall relatively easy and safe. However, a smoothcannula may not have the desired retention characteristics once thecannula has been placed through a body wall. This may present problemsas instruments and specimens are removed from a body cavity through thecannula and the associated seal systems of the trocar. It is highlydesirable for a cannula to remain fixed in the most appropriate positiononce placed. Additionally, if the Hassan technique is used, the incisionmay be larger than the cannula that may be placed through the incision.Therefore, it is necessary to provide a means to seal the incision siteafter the cannula has been inserted in order to insufflate a patient.

Many solutions to the issue of trocar-cannula fixation or stabilizationhave been formed. These solutions include an inflatable balloon attachedto the distal portion of the cannula with a thick foam bolster proximalto the insertion point into the body wall, raised threads or raisedrings associated with the outer surface of the cannula, mechanicallydeployable enlarging portions arranged at the distal end of a cannulaand suture loops or hooks associated with the proximal end of thetrocar. These solutions have provided some degree of fixation orstabilization, but they have often led to cannulas having a largeroutside diameter. Further, the thick foam bolster associated withballoon trocars has reduced the usable length of the cannula.

Some prior art balloon trocars include a natural rubber latex balloon.Other balloon trocars have balloons made of other thermoset materials ornon-distensible thermoplastic materials. Common laparoscopic surgeriesmay take up to four hours. The natural rubber latex balloons provideadequate air retention, thereby permitting proper balloon inflationduring such a surgical procedure. However, many people are allergic tolatex and may be sensitive to the balloon on the trocar. To accommodatepatients with latex allergies, some prior art balloon trocars have thelatex balloon coated with another material, such as silicone. Thesilicone coating reduces the likelihood of the patient being contactedby the latex. However, the silicone coating adds material thickness tothe device, thereby increasing the outer profile of the device. Also,the patient may still be exposed to latex if the balloon ruptures orbreaks during the surgical procedure. As a balloon trocar may be turnedand torqued against the abdominal wall or other body wall during use, aballoon having improved durability in the form of higher tensilestrength is also needed to reduce the likelihood of the balloon torupture.

There remains a need for a cannula fixation or stabilization device thatincludes a sleeve having attachment means that minimize the increase indiameter. Additionally, the cannula fixation or stabilization device mayinclude a lower profile and increase the working length of the cannula.

SUMMARY OF THE INVENTION

The invention is directed to trocars that are used in laparoscopicsurgeries and, more specifically, to balloon trocars used generallyafter the Hassan technique is used to gain entry into a body cavity,such as the abdominal cavity. The balloon at the distal portion of thetrocar provides a sealing means for the incision. Once an incision ismade to gain entry to the body cavity, the trocar is inserted throughthe incision until the balloon is within the body cavity. The balloon isthen inflated and a bolster located toward the proximal end of thecannula is moved distally along the length of the cannula in order tocompress the balloon against the inside of the body wall and seal theincision. With the bolster against the outer surface of the body wall,the balloon is maintained in compression against the inner surface ofthe body wall. In this manner, a seal is created between the balloon andthe body wall, thereby allowing a surgeon to insufflate a patient. Theballoon trocar includes a cannula assembly, a trocar seal and anobturator. The cannula assembly includes a cannula and an outer sleeve.

In one embodiment, the cannula includes a substantially longitudinaltube having a proximal end, a distal end, and a lumen extending betweenthe proximal end and the distal end. A proximal portion of the cannulahas a first, larger periphery and a distal portion of the cannula has asecond, smaller periphery. The cannula has an annular groove on theouter surface of the distal portion of the cannula toward the distal endof the cannula. The cannula also includes a plurality of channels on theouter surface of the distal portion of the cannula. The channels extendalong the length of the cannula from substantially a proximal end of thedistal portion of the cannula distally to a point proximal to theannular groove near the distal end of the cannula. The sleeve includes asubstantially longitudinal tube having a proximal end, a distal end, anda lumen extending between the proximal end and the distal end. Thesleeve also includes a proximal portion having a first, largerperiphery, a distal portion having a second, smaller periphery, and anannular groove on the outer surface of the distal portion of the sleevetoward the distal end of the sleeve. The lumen of the sleeve isconfigured to accept the cannula. The cannula assembly also includes aballoon that includes a tubular sleeve. Additionally, the cannulaassembly includes a seal. The sleeve is positioned over the cannula withthe proximal portion of the sleeve fitting over at least a distal regionof the proximal portion of the cannula and the distal portion of thesleeve fitting over at least a portion of the distal portion of thecannula. The distal end of the sleeve is positioned proximal to a distalend of the plurality of channels on the outer surface of the cannula.The cannula and the sleeve are coupled together at the proximal portionof the cannula and the proximal portion of the sleeve. The seal ispositioned between the cannula and the sleeve and compressedsufficiently to form a seal between the cannula and the sleeve. Theballoon is sufficiently long to extend between and cover the annulargroove on the outer surface of the distal portion of the cannula and theannular groove on the outer surface of the distal portion of the sleeve.An inner surface of the balloon is coated with grease. The space betweenthe outer surface of the cannula with the channels, the inner surface ofthe sleeve, the seal and the balloon forms a substantially closedchamber.

In one aspect, the proximal portion of the cannula includes asubstantially cylindrical portion having a first, larger circumferenceand the distal portion of the cannula includes a substantiallycylindrical portion having a second, smaller circumference, and theproximal portion of the sleeve includes a substantially cylindricalportion having a first, larger circumference and the distal portion ofthe sleeve includes a substantially cylindrical portion having a second,smaller circumference. In another aspect, the plurality of channels onthe outer surface of the cannula includes a plurality of substantiallylongitudinal grooves that are substantially parallel to a longitudinalaxis of the cannula. In another aspect, the seal is an o-ring, such asan o-ring made of a material having a hardness of about 40 Shore A. Inanother aspect, the seal is positioned between the proximal portion ofthe cannula and the proximal portion of the sleeve. In another aspect,the cannula includes a transition region between the proximal portion ofthe cannula and the distal portion of the cannula, the sleeve includes atransition region between the proximal portion of the sleeve and thedistal portion of the sleeve, and the seal is positioned between thetransition region of the cannula and the transition region of thesleeve. In another aspect, the cannula and the sleeve are coupledtogether at a position proximal to the seal. In another aspect, themeans for coupling the cannula to the sleeve includes a snap fittingincluding at least one projection on the outer surface of the cannulaand at least one notch on the inner surface of the sleeve. In anotheraspect, the snap fitting includes two projections positionedsubstantially circumferentially opposite each other on the outer surfaceof the cannula and two notches positioned substantiallycircumferentially opposite each other on the inner surface of thesleeve. In another aspect, the cannula assembly also includes lockingmeans to substantially prevent the cannula and the sleeve from rotatingrelative each other about a longitudinal axis of the cannula and alongitudinal axis of the sleeve. In another aspect, the locking meansincludes a projection on the outer surface of the proximal portion ofthe cannula and a channel on the inner surface of the proximal portionof the sleeve. In another aspect, the channel is substantiallylongitudinal and substantially parallel to the axis of the sleeve. Inanother aspect, the cannula assembly also includes a first winding ofthread around the balloon in the area that overlaps the annular grooveat the distal portion of the cannula and forces the balloon into thatannular groove, and a second winding of thread around the balloon in thearea that overlaps the annular groove at the distal portion of thesleeve and forces the balloon into that annular groove. In anotheraspect, the balloon includes a substantially toroid shape upon inflationof the balloon. In another aspect, the tubular sleeve of the balloonincludes an elastomeric tubular sleeve. In another aspect, theelastomeric tubular sleeve of the balloon is a silicone sleeve and thegrease is silicone grease. In another aspect, the cannula assembly alsoincludes a second tubular sleeve that is formed of an elastomericmaterial and positioned over the tubular sleeve of the balloon. Inanother aspect, the cannula assembly also includes a first winding ofthread around the balloon and second tubular sleeve in the area thatoverlaps the annular groove at the distal portion of the cannula andforces the balloon and second tubular sleeve into that annular groove,and a second winding of thread around the balloon and second tubularsleeve in the area that overlaps the annular groove at the distalportion of the sleeve and forces the balloon and second tubular sleeveinto that annular groove. In another aspect, the sleeve includes aninflation port positioned distal to the seal. In another aspect, thecannula assembly also includes a bolster that is slidably adjustablealong the length of the sleeve proximal to the balloon. In anotheraspect, the bolster includes a base, a clamping mechanism including anover-center lock design positioned at a proximal portion of the base,and a pad including a substantially incompressible gel materialpositioned at a distal portion of the base. In another aspect, thecannula assembly also includes an obturator positioned within the lumenof the cannula. The obturator includes an elongate shaft extending alonga substantially longitudinal axis between a proximal end and a distalend, a distal tip that has a prolate spheroid shape, and a handleportion having a larger periphery than the elongate shaft positioned ata proximal portion of the obturator. The shaft and distal tip of theobturator are sized and configured to slide within the lumen of thecannula. In an operative position, the distal tip of the obturator ispositioned distal to the distal end of the cannula and the handleportion of the obturator is positioned proximal to the proximal end ofthe cannula. In another aspect, the cannula assembly also includes atrocar seal positioned at the proximal portion of the cannula. Thetrocar seal includes a valve that provides an instrument seal in thepresence of an instrument and provides a zero-seal in the absence of aninstrument. In another aspect, the trocar seal is removable from thecannula assembly.

These and other features and advantages of the invention will becomemore apparent with a discussion of embodiments of the invention andreference to the associated drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a laparoscopic surgical procedure;

FIG. 2 is a plan view of a laparoscopic surgical procedure showing theplacement of trocars;

FIG. 3 is a perspective view of a prior art assembled trocar andobturator;

FIG. 4 is a perspective view of a prior art assembled trocar without anobturator;

FIG. 5 is a perspective view of a prior art cannula;

FIG. 6 is a perspective view of a prior art assembled threaded trocarand obturator;

FIG. 7 is a perspective view of a prior art threaded cannula andhousing;

FIG. 8 is a perspective view of a prior art threaded cannula;

FIG. 9 is a perspective view of a prior art cannula having an uninflatedballoon at the distal end;

FIG. 10 is a perspective view of a prior art cannula having an inflatedballoon at the distal end;

FIG. 11 illustrates a prior art trocar-cannula having a distal retentionballoon placed through a body wall in a first position;

FIG. 12 illustrates a prior art trocar-cannula having a distal retentionballoon placed through a body wall in a second position;

FIG. 13 is a perspective view of a balloon trocar having a bolster;

FIG. 14 is a perspective view of a cannula portion of the balloon trocarof FIG. 13;

FIG. 15 is a perspective view of a sleeve portion of the balloon trocarof FIG. 13;

FIG. 16 is a partial plan view in cross section depicting the cannulaportion, the sleeve portion, a seal, and an obturator of the balloontrocar of FIG. 13;

FIG. 17 illustrates a cannula assembly of the present invention placedthrough a body wall;

FIG. 18 is a partial plan view in cross section similar to FIG. 16 andincluding a port portion of the sleeve portion of the balloon trocar;

FIG. 19 is a partial plan view in cross section depicting a distalportion of the cannula portion, sleeve portion, obturator and a ballooncoupled between the cannula portion and sleeve portion by windings ofthread;

FIG. 20 is a plan view in cross section depicting the balloon trocar;

FIG. 21 is a partial plan view in cross section depicting a distalportion of the cannula portion, sleeve portion, obturator and theballoon coupled between the cannula portion and sleeve portion with aballoon having a second layer;

FIG. 22 is a perspective view of the obturator;

FIG. 23 is a perspective view of a base portion of the bolster of FIG.13;

FIG. 24 is a perspective view of a collar portion of the bolster of FIG.13;

FIG. 25 is a perspective view of a lever portion of the bolster of FIG.13;

FIG. 26 is a side view of the bolster of FIG. 13;

FIG. 27 is a perspective view of the bolster coupled to the sleeveportion of the balloon trocar;

FIG. 28 is an end perspective view of the bolster of FIG. 13;

FIG. 29 is a plan view, in cross section of a sleeve portion of theballoon trocar of FIG. 13 with an inner surface of the sleeve includingchannels;

FIG. 30 is a partial plan view in cross section depicting a distalportion of the cannula portion, sleeve portion, obturator, a ballooncoupled between the cannula portion and sleeve portion by windings ofthread, and the inner surface of the balloon coated with grease;

FIG. 31 is a partial plan view of the distal portion of the sleeveportion of the balloon trocar with the distal portion of the sleeveincluding a plurality of raised rings;

FIG. 32 is a perspective view depicting a bolster having a hollow padportion with the pad coupled to the base;

FIG. 33 is a perspective view, in cross section, depicting the bolsterof FIG. 32 with the hollow pad coupled to the base;

FIG. 34 is a perspective view depicting the bolster of FIG. 32 prior tocoupling the hollow pad to the base;

FIG. 35 is a perspective view, in cross section, depicting the bolsterof FIG. 32 prior to coupling the hollow pad to the base; and

FIG. 36 is a plan view, in cross section, depicting the bolster of FIG.32 coupled to the distal portion of the sleeve portion of the balloontrocar.

DESCRIPTION

With reference to FIGS. 1 and 2, a typical laparoscopic procedure isillustrated where a plurality of trocars 100 are placed through a bodywall 50, such as an abdominal wall, and into a body cavity 52, such asan abdominal cavity. The body cavity 52 is insufflated, or inflated withgas, to distend the body wall 50 and provide a working space for thelaparoscopic procedure. The trocars 100 each include a cannula 110 and aseal 150. Positive pressure is maintained within the body cavity 52 bythe seal 150 associated with the cannula 110. In addition, the cannula110 must form a gas-tight seal against adjacent tissue. If positivepressure is lost, either through the seal 150 associated with thecannula 110 or the seal between the cannula and the adjacent tissue, theprocedure may be compromised.

As the body cavity 52 is inflated, the body wall 50 may be greatlydistended. The access sites may tend to enlarge under the distention ofthe body wall 50 and compromise the positioning and sealing of thecannula 110. As stated above, the manipulation of instruments 190 usedthrough the trocars 100 may result in movement of the cannulas 110 ineither a proximal or distal direction within the access site through thebody wall 50. As this occurs, some liquefaction may take place and thepreferred relationship between the cannula 110 and the body tissue maybe compromised.

Referring now to FIGS. 3-5, a typical assembled trocar 100 is shownhaving a cannula 110, a seal housing 150 and an obturator 160. Thecannula 110 typically has a smooth exterior surface 102 so that it maybe inserted through the body wall 50 easily. The seal housing 150contains a seal system that prevents retrograde gas-flow. The obturator160 is a cutting or piercing instrument that creates the pathway throughthe body wall 50 through which the cannula 110 follows. Surgicalobturators 160 are generally sized and configured to create a defect intissue that is appropriate for the associated cannula 110. However, thedefect may have a tendency to enlarge during a surgical procedure as thetrocar 100 or cannula 110 is manipulated. As an instrument 190 is urgeddistally and proximally, or inserted and withdrawn, the cannula 110 maymove or even be inadvertently withdrawn due to the friction between theinstrument 190 and the seal 150 of the trocar housing.

With specific reference to FIGS. 6-8, a trocar 100 or access device isshown where the outer surface 102 of the cannula 110 includes aplurality of raised features 115. These raised features 115 are sizedand configured to increase resistance to proximal and distal motion asinstruments 190 are maneuvered, and especially as specimens are removed,through the trocar 100. The prior art includes either sequential raisedrings or a raised coarse-thread 115. The rings or threads 115 are thesame size and height along the length of the cannula 110. While therings or threads 115 of the prior art may stabilize the cannula 110 tosome degree, they do not necessarily seal the cannula 110 against theadjacent tissue of a body wall 50. There may be gas loss associated withthe use of these systems. Due to the height of the raised rings orthreads 115, increased insertion force is required to penetrate a bodywall 50. The insertion force may be reduced in the instance of acontinuous coarse thread 115 in comparison to a sequence of discreteraised rings or features as a threaded cannula 110 may actually be“screwed” into the tissue defect in accordance with the thread directionand pitch, rather than pushed through without appropriate rotation.

With reference to FIGS. 9-12, a surgical access device 100 according toprior art includes a cannula 110 having an inflatable balloon 120associated with the distal-end portion 122 of the cannula. The balloon120 is sized and configured to fit snugly around the cannula 110 in theuninflated condition. The balloon 120 is inflated after the cannula 110is properly placed through the body wall 50 and into the body cavity 52.The balloon 120 is generally held against the interior surface 54 of thebody wall 50 by a counter-force that is associated with a slidingcounter-force member, such as a foam bolster 180. The bolster 180 isassociated with the proximal portion of the cannula 110. The balloons120 associated with the devices of the prior art are typically“thick-walled” structures constructed as part of the cannula 110. Theballoon 120 is generally bonded to the distal-end portion 122 of thecannula 110 and an inflation channel or lumen is provided within thewall of the cannula 110.

Referring to FIG. 13, one embodiment of the balloon trocar 200 includesa cannula assembly 210, a trocar seal 220 and an obturator 230. Thecannula assembly 210 includes a cannula 250 and an outer sleeve 300.

Referring to FIG. 14, the cannula 250 includes a substantiallylongitudinal tube 252 having a proximal end 254, a distal end 256, and alumen 258 therebetween. The cannula 250 may include at least a proximalportion 260 having a first, larger periphery and a distal portion 262having a second, smaller periphery. In one embodiment, the proximalportion 260 and distal portion 262 of the cannula 250 may each include asubstantially cylindrical portion, with the proximal portion 260 havinga first, larger circumference and the distal portion 262 having asecond, smaller circumference. The cannula 250 may also include atransition region 264 between the proximal portion 260 and the distalportion 262. The lumen 258 of the cannula 250 may be substantiallysmooth and configured to accept the obturator 230 (see FIG. 13). Theproximal portion 260 of the cannula 250 may be configured to accept thetrocar seal 220 (see FIG. 13). The outer surface of the distal portion262 of the cannula 250 includes an annular groove 266 toward the distalend 256 of the distal portion of the cannula. The annular groove 266 maylie within a plane that is substantially perpendicular to a longitudinalaxis 272 of the cannula 250. Additionally, the outer surface of thedistal portion 262 of the cannula 250 includes a plurality of channels268 extending along the length of the cannula from substantially theproximal end of the distal portion of the cannula distally to a pointproximal to the annular groove 266 near the distal end 256 of the distalportion of the cannula. The plurality of channels 268 is adapted tofacilitate the flow of gasses or fluids therethrough. In one embodiment,the plurality of channels 268 may include a plurality of substantiallylongitudinal grooves 270 that are substantially parallel to thelongitudinal axis 272 of the cannula 250. In one embodiment, the cannula250 may be made of a polymeric material, such as a polycarbonatematerial.

Referring to FIG. 15, the outer sleeve 300 of the cannula assembly 210includes a substantially longitudinal tube 302 having a proximal end304, a distal end 306, and a lumen 308 therebetween. The sleeve 300 mayalso include at least a proximal portion 310 having a first, largerperiphery and a distal portion 312 having a second, smaller periphery.In one embodiment, the proximal portion 310 and distal portion 312 ofthe sleeve 300 may each include a substantially cylindrical portion,with the proximal portion 310 having a first, larger circumference andthe distal portion 312 having a second, smaller circumference. Thesleeve 300 may include a transition region 314 between the proximalportion 310 and the distal portion 312. The lumen 308 of the sleeve 300is configured to accept the cannula 250 (see FIG. 13) and may besubstantially smooth. An outer surface 322 of the distal portion 312 ofthe sleeve 300 includes an annular groove 316 toward the distal end 306of the distal portion of the sleeve. The annular groove 316 may liewithin a plane that is substantially perpendicular to a longitudinalaxis 320 of the sleeve 300. In one embodiment, the sleeve 300 may bemade of a polymeric material, such as a polycarbonate.

Referring again to FIG. 13, with the sleeve 300 positioned over thecannula 250, the proximal portion 310 of the sleeve 300 fits over atleast a distal region of the proximal portion 260 of the cannula and thedistal portion 312 of the sleeve fits over at least a portion of thedistal portion 262 of the cannula. Additionally, with the sleeve 300positioned over the cannula 250, the distal end 306 of the sleeve 300 ispositioned proximal to a distal end of the plurality of channels 268 onthe outer surface of the cannula 250.

As stated above, the cannula assembly 210 includes the cannula 250 andthe sleeve 300. Referring now to FIG. 16, to substantially prevent gasor fluid from leaking between the proximal end 304 of the sleeve 300 andthe proximal portion 260 of the cannula 250, a seal, such as an o-ring350, may be positioned between the cannula and the sleeve. In oneembodiment the seal, such as the o-ring 350, is positioned between theouter surface of the cannula 250 and the inner surface of the sleeve300. In another embodiment, the outer surface of the distal region ofthe proximal portion 260 of the cannula 250 may include a substantiallyflat surface, such as a planar surface or a chamfered surface, whichcommunicates between the proximal portion 260 of the cannula and eitherthe transition region 264 or the distal portion 262 of the cannula.Similarly, the inner surface of the distal region of the proximalportion 310 of the sleeve 300 may include a substantially flat surface,such as a planar surface or a chamfered surface, which communicatesbetween the proximal portion 310 of the sleeve and either the transitionregion 314 or the distal portion 312 of the sleeve. In the embodimentdepicted, the seal, such as the o-ring 350, is positioned between theflat surface on the outer surface of the distal region of the proximalportion 260 of the cannula 250 and the flat surface on the inner surfaceof the distal region of the proximal portion 310 of the sleeve 300.

Referring to FIGS. 13-17, the cannula 250 and the sleeve 300 are coupledtogether at the proximal portion 260 of the cannula and the proximalportion 310 of the sleeve at a position proximal to the seal, such asthe o-ring 350. In one embodiment, the means for coupling the proximalportion 260 of the cannula 250 and the proximal portion 310 of thesleeve 300 includes a snap fitting 360 having at least one projection362 on the outer surface of the cannula and at least one notch 364 onthe inner surface of the sleeve. Alternatively, the projection may be onthe inner surface of the sleeve and the notch may be on the outersurface of the cannula. The at least one projection 362 and the at leastone notch 364 are positioned such that when the projection is positionedwithin the notch, the seal, such as the o-ring 350, is compressedsufficiently to form a seal between the cannula 250 and the sleeve 300.In one aspect, the seal, such as the o-ring 350, is made from a soft,compressible material, such as a silicone having a hardness of about 40Shore A. In one aspect, the snap fitting 360 includes two projections362 positioned substantially circumferentially opposite each other onthe outer surface of the cannula 250 and two notches 364 positionedsubstantially circumferentially opposite each other on the inner surfaceof the sleeve 300. Other means for coupling the sleeve 300 to thecannula 250 that are well known in the art may also be used, such asother mechanical means or adhesive bonding.

Referring to FIGS. 14, 15 and 18, the cannula assembly 210 also includesa locking means 370 to substantially prevent, or minimize, the cannula250 and the sleeve 300 from rotating relative each other about thelongitudinal axes 272, 320 while the cannula and sleeve are coupledtogether. In one embodiment, the locking means 370 includes a projection372 on the outer surface of the cannula 250 and a channel 374 on theinner surface of the sleeve 300. In one embodiment, the projection 372is positioned on the outer surface of the proximal portion 260 of thecannula 250 and the channel 374 is positioned on the inner surface ofthe proximal portion 310 of the sleeve 300 and extends to the proximalend 304 of the sleeve. Alternatively, the projection 372 may bepositioned on the inner surface of the proximal portion 310 of thesleeve 300 and the channel 374 may be positioned on the outer surface ofthe proximal portion 260 of the cannula 250. If the channel 374 ispositioned on the sleeve 300, the channel may either be through theentire thickness of the wall of the sleeve or through only a portion ofthe thickness of the wall of the sleeve. To substantially prevent orminimize rotation between the cannula 250 and the sleeve 300, thechannel 374 is substantially longitudinal and substantially parallel tothe axis 320 of the sleeve 300. The projection 372 may include any shapethat fits within the walls of the channel 374 and facilitates theprevention or minimization of rotation between the cannula 250 and thesleeve 300. In one embodiment, the projection 372 is substantiallycylindrical while in another embodiment the projection is substantiallyrectangular.

Referring to FIG. 19, the cannula assembly 310 also includes a balloon400. In one aspect, the balloon includes a tubular sleeve 402. Thetubular sleeve 402 may include an elastomeric material. Elastomericmaterials that may be used to make the balloon 400 include silicone,polyisoprene, and urethane. Alternatively, the balloon 400 may be madeof other materials, such as MYLAR, that may be folded onto the cannula250 and sleeve 300 and inflated into a larger profile. The balloon 400may be cut to length prior to installation onto the cannula 250 andsleeve 300 such that the balloon is sufficiently long to extend betweenand cover the annular grooves 266, 316 at the distal portions 262, 312of the cannula and sleeve. The balloon 400 is slid over the distal end256 of the cannula 250 and the distal end 306 of the sleeve 300 until itcovers the annular grooves 266, 316 in the cannula and sleeve.

In one aspect, the balloon 400 is fixed in place by winding thread 404around the balloon in the areas that overlap of the annular grooves 266,316 at the distal portions 262, 312 of the cannula 250 and sleeve 300.Winding the balloon 400 with thread 404 forces the portion of theballoon that overlaps the annular grooves 266, 316 into the annulargrooves and holds the balloon in place, thereby substantially preventinglongitudinal, axial movement of the balloon along the cannula assembly.The grooves 266, 316 are of sufficient depth that forcing the balloon400 into the annular grooves 266, 316 makes the balloon and winding 404substantially flush to the cannula 250 and sleeve 300 at the windings,thereby making the cannula assembly 210 substantially smooth.Furthermore, forcing the balloon 400 into the annular grooves 266, 316with the windings 404 also forms a seal between the balloon and thecannula 250 and between the balloon and the sleeve 300.

Referring to FIG. 20, the space between the outer surface of the cannula250 with the channels 268 (see FIG. 14), the inner surface of the sleeve300, the o-ring 350, and the balloon 400 with the windings 404 form asubstantially closed chamber 408. In one aspect, the channels 268 on theouter surface of the cannula 250 are formed into the wall of the cannulaso as not to increase the overall thickness of the wall of a standardcannula. The lumen 308 of the sleeve 300 may be configured to provideminimal space between the distal portion 312 of the sleeve and thedistal portion 262 of the cannula 250, thereby minimizing the overallprofile of the cannula assembly 210. The gap between the transitionregions 264, 314 of the cannula 250 and the sleeve 300 may be largerthan the gap between the distal portions 262, 312 in order to moreevenly distribute gas or fluid through the channels 268 on the outersurface of the cannula 250 during inflation and deflation of theballoon.

The balloon 400 may be made to take on one of many different shapes uponinflation of the balloon. In one aspect, the balloon 400 may include asubstantially toroid shape upon inflation. In another aspect, theballoon 400 may include a disc shape upon inflation. In another aspect,the balloon 400 may be a fluted balloon. In one aspect, different shapesfor the balloon 400 may be attained by varying the thickness about thetubular sleeve 402 that forms the balloon or by pre-molding a differentshape for the balloon.

The balloon 400 should have sufficient impermeability properties tosubstantially prevent inflation gas or fluid from permeating through awall of the balloon. Additionally, the balloon should bias toward adeflated state during deflation of the balloon. Referring to FIG. 21,when using a balloon material that does not possess adequate propertiesto bias the balloon toward deflation, an outer layer 406 may bepositioned and fixed over the balloon. The outer layer 406 may includesilicone, latex, polyisoprene, rubber, or other biocompatibleelastomeric materials that are well known in the art. The outer layer406 may be wound onto the cannula 250 and sleeve 300 together with theballoon 400, as described above.

Some elastomeric materials for the balloon 400 possess inadequateimpermeability properties to enable balloons made of such materials tobe used without first sealing the pores in the balloon material. Forexample, a silicone balloon 400 has adequate properties to bias theballoon toward deflation, but depending on the grade of silicone it maybe too porous to maintain adequate inflation for the term of a surgicalprocedure. Referring to FIG. 30, in one aspect the inner surface 560 ofthe balloon 400 is coated with grease 562 to seal the pores in theballoon. For example, the balloon 400 may be formed of a poroussilicone, and the grease 562 may be silicone grease By sealing thepores, the grease 562 extends the inflation time of the balloon.

With continued reference to FIG. 30, the grease 562 provides additionaladvantages as well. To prevent or minimize the likelihood of a creaseforming and creating a leak path when winding the ends of the balloon400 with the winding 404, the periphery of the inside surface 560 of theballoon should be about equal to, or smaller than, the periphery of theannular groove 266 on the cannula 250. In this manner, the balloon isstretched onto the cannula 250 and sleeve 300 and the ends of theballoon 400 fit snugly into the annular grooves 266, 316 of the cannulaand sleeve. With the balloon being stretched in the area of the annulargrooves 266, 316, it is not likely that the balloon 400 will crease whenthe windings 404 are applied to the balloon. However, the stretchingaction to place the balloon 400 onto the cannula 250 and sleeve 300 maycause uneven stretching about the perimeter of the balloon that mayresult in asymmetric inflation of the balloon. By applying grease 562 tothe inner surface 560 of the balloon 400 prior to placing the balloononto the cannula 250 and sleeve 300, the grease acts as a lubricant andpermits the balloon to slide more easily over the cannula and sleeve,thereby facilitating assembly of the trocar, and to rotate back toward anatural position about the perimeter of the balloon, thereby providingfor substantially symmetric inflation of the balloon. In other words,the grease 562 allows the balloon to substantially self-center itself,thereby substantially equalizing the stresses within the balloonmaterial and allowing for substantially symmetric inflation of theballoon.

Another advantage provided by applying the grease 562 to the innersurface of the balloon 400, rather than adding an additional layer tothe balloon, is it minimizes any increase in the outer profile of theballoon. A further advantage of using a silicone balloon 400 with thesilicone grease 562 is it does not introduce patients to materials thatthey may be allergic to, such as latex.

In one aspect, the balloon trocar 200 includes a balloon 400 made ofdistensible thermoplastic elastomeric (TPE) materials, such asstyrene-ethylene-butylene-styrene (SEBS) tri-block polymer. One suchSEBS tri-block polymer is CILRAN, a distensible thermoplasticmanufactured by Randolph Austin Industries of Austin, Tex. CILRANballoons provide increased gas retention and improved durability overballoons made of thermoset materials.

Balloon trocars are designed such that the balloon may remain inflatedduring the duration of a laparoscopic surgery, which may last up to fourhours, or sometimes more. The gas leakage parameters required during alaparoscopic surgery may dictate that the diameter of the inflatedballoon have less than about forty percent reduction over a four hourperiod following the removal of the inflation source. During testing,the diameter of an inflated CILRAN balloon 400 reduced only about fourpercent over four hours. The CILRAN balloon 400 does not require anyadditional coatings to attain the desired permeability properties forballoons used for balloon trocars. Nevertheless, the inner surface ofthe CILRAN balloon 400 may be coated with grease, or other lubricant, tofacilitate assembly of the balloon trocar 200. It was also discoveredduring testing that CILRAN produces a highly durable balloon. The highdurability is attributed to the higher tensile strength of the CILRANover latex. The higher tensile strength allows the CILRAN balloons toendure higher pressures during use.

The CILRAN balloon 400 may be produced by providing an extruded CILRANtube. The CILRAN tubing, in its original state, may possess unevenstress due to its molecular structure that causes the tubing to inflateasymmetrically. To condition the CILRAN tubing so that it will inflatesymmetrically, tubing may be provided that is about one-half thefinished outer diameter of the balloon 400 in the uninflated conditionand about twice the wall thickness of the finished balloon in theuninflated condition. The tubing is inflated with air beyond its yieldpoint such that when the air is released from the tube, the balloon 400relaxes at a condition where it is at about its finished outer diameterand finished wall thickness. Inflating the tube beyond its yield pointbreaks apart molecular clusters within the CILRAN tube, making it easierto control symmetry of the balloon 400 when inflated subsequently. Inone aspect, the CILRAN tubing may be inflated to about three times itsoriginal diameter. The tubing may be annealed in an oven following theinflation and subsequent relaxation to prevent the tubing fromreassuming its original pre-inflated size. Annealing the tubing may beperformed at about 70° C. for at least about one hour. The annealinghelps relax the molecules in the tubing, thereby preventing the tubingfrom assuming its original size after being stretched beyond its yieldpoint.

Another method of producing the CILRAN balloon 400 includes providing anextruded CILRAN tube having a diameter that is about the finisheduninflated diameter of the balloon and a wall thickness that is aboutthe finished wall thickness of the uninflated balloon. The tube isstretched longitudinally beyond its yield point. Stretching the CILRANtubing longitudinally aligns the molecular structure of the tubinglongitudinally, which facilitates symmetric inflation of the tubing. TheCILRAN tubing may also be processed through a combination of theinflation and longitudinal stretching that is stated above.

The properties of CILRAN and other thermoplastic elastomers can bemodified by removing plasticizing agents from the material, or by addingplasticizing agents, such as mineral oils and silicone oils, to thematerial. The addition of plasticizing agents can reduce the durometerrating of the material, reduce the tensile strength of the material,increase elongation of the material, and reduce surface roughness of thematerial Removing plasticizing agents from the CILRAN thermoplasticelastomeric material increases the durometer rating of the material,increases the tensile strength of the material and reduces elongation ofthe material.

The thermoplastic balloons 400, such as the CILRAN balloons, may becoupled to a surgical device, such as a trocar cannula 250, withtechniques that are either not possible or not practicable withthermoset materials. These coupling techniques take advantage of theability of the thermoplastic elastomeric balloon to bond to trocars andother medical devices that are made of other thermoplastic materialsthrough localized heating and melting. Examples of processes that makeuse of this property include ultrasonic welding, heat staking andwelding, solvent bonding, and insert molding, as well as other processesthat are well known in the art.

Those with ordinary skill in the art will recognize that otherthermoplastic elastomers and thermoplastic polyurethane elastomers (TPU)will work well for balloon trocars and other surgical devices thatutilize balloons and are, therefore, contemplated as within the scope ofthe invention. Such materials include SANTOPRENE, C-FLEX, and DYNAFLEX,to name a few. Other thermoplastic materials, such as KRATON or SEBS,have been shown to have similar properties to CILRAN.

Referring again to FIG. 18, the sleeve 300 includes an inflation port380 positioned to be distal to the seal, such as the o-ring 350. Theinflation port 380 provides a pathway for gas or fluid to be introducedand removed from the chamber 408. The inflation port 380 may include anormally closed check valve 382 having a spring-loaded plunger 384. Thecheck valve 380 may include a Luer lock 386. It is contemplated thatother inflation ports that are well known in the art may be used.

Referring again to FIG. 13, the trocar seal 220 may include a valve thatprovides an instrument seal in the presence of an instrument, such asthe obturator 230, and a zero-seal in the absence of an instrument. Thetrocar seal 220 may also be removable from the cannula assembly 210.Removal of the trocar seal 220 is useful for tissue removal through thecannula assembly 210 and for rapid release of insufflation gasses.

Referring to FIG. 22, the obturator 230 includes an elongate shaft 232extending along a substantially longitudinal axis 234 between a proximalend 236 and a distal end 238. A distal tip 240 of the elongate shaft 232may include a prolate spheroid shape. The elongate shaft 232, includingthe distal tip 240, is adapted to be removably positioned within thelumen 258 of the cannula 250 (see FIGS. 14, 16 and 19). Moreparticularly, the elongate shaft 232 is sized and configured to slidewithin the lumen 258 of the cannula 250. A proximal portion 242 of theobturator 230 may include a handle portion 244 having a larger peripherythan the elongate shaft 232 to facilitate advancing and retracting theobturator within the lumen 258 of the cannula 250. In an operativeposition, the distal tip 240 of the obturator 230 is positioned distalto the distal end 256 of the cannula 250 and the handle portion 244 ofthe obturator is positioned proximal to the proximal end 254 of thecannula.

The obturator 230 may be made of a polymeric material, such as apolycarbonate. Those with ordinary skill in the art will recognize thatthe obturator 230 may be made of other materials that are well known inthe art and are considered within the scope of the present invention. Incomparison to obturators having distal tips with a spheroid shape, thedistal tip 240 of the obturator 230 having a prolate spheroid shaperequires a lower insertion force to insert the trocar into a bodythrough an incision within a body wall. The prolate spheroid shape ofthe distal tip 240 of the obturator 230 also reduces the likelihood ofinjuring tissue or organs within the body cavity, in comparison toobturators having distal tips with a more pointed shape. Using theobturator 230 having a distal tip 240 with a prolate spheroid shape, thesurgeon can merely nick the peritoneum and dilate or stretch theincision open with the distal tip of the obturator.

Referring again to FIG. 13, a bolster 410 may be used in conjunctionwith the balloon trocar 200 to assist the balloon 400 (FIG. 19) to sealaround an incision in the body wall 50 through which the balloon trocaris to be inserted with the balloon sealing the incision from within thebody cavity 52. The bolster 410 is configured to perform as a cannulafixation device on the outside of the body while the balloon 400 acts asa cannula fixation device on the inside of the body. The bolster 410 isslidably adjustable along the length of the cannula assembly 210proximal to the balloon 400 and includes a clamping device 415 forlocking the bolster in position along the length of the cannulaassembly. The balloon 400 (FIG. 19), on the other hand, is fixed at alocation along the length of the cannula assembly 210 and seals againstthe inner surface of the abdominal wall.

To facilitate the clamping features of the bolster 410, the bolsterincludes a base 420 and a clamping mechanism 415. The clamping mechanism415 includes an adjustable collar 460 and a lever 500. The clampingfeatures may utilize an over-center lock design to maintain the bolster410 in a fixed position along the length of the cannula assembly 210.The bolster also includes a pad 530 that, in one aspect, seals againstthe body wall.

Referring to FIG. 23, the base 420 includes a sleeve 422 projectingdistally from a first, proximal flange 424. The proximal flange 424includes a proximal surface 428 and a distal surface 430. The proximalsurface 428 and the distal surface 430 of the proximal flange 424 aresubstantially parallel to each other and substantially perpendicular toan axis 432 of the base 420. Although the proximal flange 424 is shownas being flat, other shapes, such as rounded shapes, may be used and arecontemplated as within the scope of the invention. The sleeve 422portion of the base 420 includes a proximal end 434, a distal end 436,and a lumen 438 therebetween. The lumen 438 is sized to receive andslidably engage the sleeve 300 of the cannula assembly 210. An outersurface 440 of the sleeve 422 portion of the base 420 may include asubstantially cylindrical shape. The lumen 438 of the sleeve 422 portionof the base 420 extends through the proximal flange 424, thereby formingan aperture 442 in the proximal flange.

A clamp receptacle 444 extends proximally from the proximal surface 428of the first, proximal flange 424. The clamp receptacle 444 includes atleast one riser 446 extending from the proximal surface 428 of theproximal flange 424 and a platform 448 extending from the at least oneriser 446. In one aspect, the clamp receptacle 444 includes a firstriser 450 and a second riser 452 with the platform 448 extending betweenthe first and second risers. The platform 448 is shaped so as to notextend over the aperture 442 in the proximal flange 424. In other words,the platform 448 provides clearance for the cannula assembly 210 suchthat the bolster 410 may slidably engage the cannula assembly withoutthe platform interfering with the engagement. The platform 448 includesa distal surface 454 that is substantially parallel to the proximalsurface 428 of the proximal flange 424. As will be described below, thedistance between the distal surface 454 of the platform 448 and theproximal surface 428 of the proximal flange 424 is sufficient to receivethe clamp mechanism 415 portion of the bolster 410. The distal surface454 of the platform includes a substantially linear slot 456 extendingradially therethrough. In one aspect, the base may be made of apolymeric material, such as a polycarbonate. However, it is contemplatedthat other materials, such as metals and composites, may be used.

Referring to FIG. 24, the collar 460 portion of the clamping mechanism415 of the bolster 410 includes a substantially circumferential ring 462defining a split 464. The collar 460 further includes a proximal end466, a distal end 468, and an inner surface 470. The inner surface 470of the collar 460 may include a counterbore configuration forming aledge 472 therein. The split 464 in the collar 460 forms a first end 474of the collar 460 and a second end 476 of the collar. The collar 460 isflexible in order to adjust the fit of the collar over the cannulaassembly 210. More particularly, the first end 474 and the second end476 of the collar may be brought closer together to create sufficientfriction between the clamping mechanism 415 of the bolster 410 and thecannula assembly 210 to substantially fix the bolster in place along thelength of the cannula assembly. The first end 474 and the second end 476of the collar may also be spread apart to reduce or substantiallyeliminate the friction between the bolster 410 and the cannula assembly210 so that the bolster may slide along the length of the cannulaassembly.

To facilitate control of the distance between the first end 474 and thesecond end 476 of the collar 460, a first tab 478 extends from the firstend 474 of the collar and a second tab 480 extends from the second end476 of the collar. In one aspect, the first and second tabs 478, 480 mayextend circumferentially from the first and second ends 474, 476,respectfully. Alternatively, the first and second tabs 478, 480 mayextend tangentially or radially from the first and second ends 474, 476,respectfully, or in any other manner that is well known in the art. Thefirst tab 478 includes a first aperture 482 extending longitudinallytherethrough and the second tab 480 includes a second aperture 484extending longitudinally therethrough. The first and second apertures482, 484 extend substantially parallel to an axis 486 of the collar 460.As will be discussed below, the lever 500 interacts with the tabs 478,480 to control the distance between the first and second ends 474, 476of the collar 460. The collar may be made of a polymeric material, suchas polycarbonate or high density polyethylene (HDPE) However, it iscontemplated that other materials, such as metals and composites, may beused.

Referring to FIG. 25, the lever 500 includes an arm 502 having a first,proximal surface 504, a second, distal surface 506, a first end 508 anda second end 510. The proximal and distal surfaces 504, 506 of the arm502 are substantially parallel to each other. A substantiallycylindrical first pin 512 extends proximally from the proximal surface504 of the arm 502 proximate the first end 508 and a substantiallycylindrical second pin 514 extends distally from the distal surface 506proximate the first end. The first and second pins 512, 514 each extendsubstantially perpendicular from the proximal and distal surfaces 504,506, respectively, of the arm 502. An axis 516 of the first pin 512 andan axis 518 of the second pin 514 are substantially parallel to eachother, but are also offset from each other. In one aspect, the first pin512 is closer to the first end 508 of the arm 502 than is the second pin514. The peripheries of the first and second pins 512, 514 are sized tofit within the first and second apertures 482, 484, respectively, of thetabs 478, 480 of the collar 460. In one aspect, there may be a tab 520positioned at the second end 510 of the arm 502 to facilitate rotationof the lever 500 when it is assembled into the bolster 410.

Referring to FIG. 26, there is a space 488 between a distal surface ofthe first tab 478 of the collar 460 and a proximal surface of the secondtab 480 of the collar. In one aspect, the distal surface of the firsttab 478 and the proximal surface of the second tab 480 are substantiallyflat, substantially parallel to each other and substantiallyperpendicular to the axis 486 of the collar 460. The space 488 is sizedto receive the arm 502 of the lever 500. The lever 500 is coupled to thecollar 460 by manipulating the arm 502 of the collar into the space 488between the first and second tabs 478, 480 of the collar and insertingthe first pin 512 of the lever into the first aperture 482 (see FIG. 24)in the first tab 478 of the collar 460 and inserting the second pin 514(see FIG. 25) of the lever into the second aperture 484 (see FIG. 24) inthe second tab 480 of the collar. In this manner, the lever 500 ispivotally coupled to the collar 460. In one aspect, the first pin 512 ofthe lever is sufficiently long to extend beyond the proximal surface ofthe first tab 478 of the collar 460, while the second pin 514 issubstantially flush or below flush with the distal surface of the secondtab 480 of the collar.

With reference to FIG. 27 and continued reference to FIG. 26, to couplethe clamping mechanism 415, including the collar 460 and lever 500, tothe base 420, the collar and lever are inserted into the clampreceptacle 444 portion of the base. More particularly, the clampingmechanism 415 is inserted between the proximal surface 428 of theproximal flange 424 portion of the base 420 and the distal surface 454of the platform 448 of the clamp receptacle 444 portion of the base suchthat the collar 460 is nested between the proximal flange 424, theplatform 448, and the at least one riser 446 portion of the clampreceptacle 444. Further, the first and second tabs 478, 480 of thecollar 460 and the first and second pins 512, 514 (see FIGS. 24 and 25)of the lever 500 are positioned between the proximal surface 428 of theproximal flange 424 portion of the base 420 and the distal surface 454of the platform 448. The distance between the proximal surface 428 ofthe proximal flange 424 portion of the base 420 and the distal surface454 of the platform 448 is sufficient for the clamp mechanism 415 toslidably engage within the clamp receptacle 444, yet also sufficientlylow to maintain the lever 500 and collar 460 of the clamp mechanism 415in an engaged relationship with each other during activation of thelever to maintain the clamping force of the collar against the cannulaassembly 210. In one aspect, the first pin 512 of the lever 500, whichextends proximally beyond the proximal surface of the first tab 478, ispositioned within the slot 456 on the distal surface 454 of the platform448 to facilitate maintaining the position of the first and second tabs478, 480 of the collar 460 and the first and second pins 512, 514 of thelever 500 between the proximal surface 428 of the first, proximal flange424 portion of the base 420 and the distal surface 454 of the platform448.

Referring to FIGS. 13, 23 and 27, the bolster 410 is slidably mountedonto the cannula assembly 210 by inserting the distal end 256 of thecannula distally through the proximal end 466 of the collar 460, throughthe aperture 442 of the first, proximal flange 424 of the base 420, andthrough the sleeve 422 of the base. The bolster 410 and cannula assembly210 are slid relative to each other until the distal end 436 of thesleeve 422 of the base 420 is proximal to the balloon 400 (see FIG. 19).

Referring to FIG. 28, when viewing the proximal end 466 of the collar460 and lever 500 (looking distally), in one aspect the distance betweenthe first and second ends 474, 476 of the collar is at its maximum whenthe lever is in a first, clockwise position. Those with ordinary skillin the art will recognize that the collar 460 and lever 500 may bereversed so that the distance between the first and second ends 474, 476of the collar is at its maximum when the lever is in counter clockwiseposition. Rotating the lever 500 in a counter clockwise direction movesthe first and second ends 474, 476 of the collar 460 closer together;thereby reducing the circumference of the collar and tightening thecollar against the cannula assembly 210 (see FIG. 13). The change incircumference of the collar 460 as the lever 500 is rotated is caused bythe offset between the first pin 512 and the second pin 514 of the lever(see FIG. 25). The circumference of the collar 460 is at its smallestwhen the lever is rotated about 180° from the first position. Tofacilitate the over-center lock design features of the clampingmechanism 415, the lever 500 is rotated from the first position morethan about 180° to a second position. In this manner, as the lever 500is rotating from the first position, the circumference of the collar 460reduces until the lever has rotated about 180°, then expands slightlyuntil the lever is positioned at the second position. With the lever 500in the second position, higher pressure is initially required to rotatethe lever away from the second position in a clockwise direction to thefirst position because the circumference of the collar 460 is reduceduntil the lever reaches the position that is about 180° from the firstposition. The higher pressure that is required protects againstinadvertent release of the clamp mechanism 415. Although the clampmechanism 415 was described in detail, those with ordinary skill in theart will recognize that other clamp mechanisms that are well known inthe art may be used with satisfactory results.

Referring further to FIGS. 13 and 28, the inner surface 470 of thecollar may clamp directly against an outer surface 322 of the sleeve 300portion of the cannula assembly 210. Alternatively, the bolster 410includes a flexible ring 490 positioned inside the collar 460. The ring490 may be seated against the ledge 472 (FIG. 24) on the inner surface470 of the collar 460. The inner surface 492 of the ring 490 is sized topermit the bolster 410 to slide along the cannula assembly 210 when thelever 500 is in the first position and to be pressed against the outersurface 322 of the sleeve 300 portion of the cannula assembly when thelever is in the second position. In this manner, the ring 490 ensuresthat there is sufficient friction between the clamping mechanism 415 ofthe bolster 410 and the cannula assembly 210 when the lever is in thesecond position to maintain the position of the bolster along thecannula assembly. In one aspect, the ring 490 is made of anincompressible elastomeric material, such as silicone. In one aspect,the ring 490 is molded from a soft elastomeric material, such as asilicone having a hardness of about 40 Shore A durometer. Alternatively,the ring 490 may be made of harder polymers, such as polycarbonate,high-density polyethylene (HDPE), or acrylonitrile butadiene styrene(ABS). Those with ordinary skill in the art will recognize that othermaterials that are well known in the art may be used and arecontemplated to be within the scope of the invention.

With the bolster 410 mounted onto the cannula assembly, the ring 490makes the collar 460 substantially self-centering around the cannulaassembly 210. Having the first pin 512 of the lever 500 extending intothe slot 456 on the distal surface 454 of the platform 448 substantiallyprevents the clamping mechanism 415 from rotating about the base 420when the bolster is positioned on the cannula assembly 210 and the lever500 is in the second position. This in turn substantially prevents thebolster 410 from rotating about the cannula assembly 210.

To provide additional friction between the bolster 410 and the cannulaassembly 210, the outer surface 322 of the outer sleeve 300 may includea plurality of raised annular rings 340 (see FIG. 31) spacedlongitudinally along its length. Individual rings 340 may each liewithin a plane that is substantially perpendicular to the longitudinalaxis 320 of the sleeve 300. The distance between adjacent rings 340 maybe about twice the longitudinal length of the rings, or other suitabledistance. The cross section of the outer rings 340 may have shapes otherthan annular, or circular, such as rectangular, triangular, polygonal,elliptical, etc. The outer sleeve 300 includes a distal taper such thatthe proximal end 342 (FIG. 15) of the distal portion 312 of the outersleeve has a larger diameter than the distal end 306 of the distalportion of the outer sleeve. The rings 340 may be either concentric withthe distal portion 312 of the outer sleeve 300, as depicted in FIG. 31,or non-concentric with the distal portion of the outer sleeve. The rings340 also produce a distal taper, such that the diameter of the raisedrings toward the distal end 306 of the sleeve 300 is smaller than thediameter of the raised rings toward the proximal end 304 of the sleeve,but the distal taper of the rings is smaller than the distal taper ofthe distal portion 312 of the sleeve 300. In this manner, the ringheights, or the radial distance between the outer surface 322 of thedistal portion 312 of the outer sleeve 300 and the outer perimeter ofthe rings 340, decrease proximally. More particularly, the ring heightsare larger toward the distal end 306 of the sleeve 300 and smallertoward the proximal end 304 of the sleeve. The ring height of thedistal-most ring 340 of the sleeve is about 0.13 mm (0.005 inch), butmay be larger or smaller. Those with ordinary skill in the art willrecognize that the raised rings 340 may have the same taper as thedistal portion 312 of the outer sleeve or have equal diameters along thelength of the distal portion of the outer sleeve.

With the outer sleeve 300 having a distal taper and the ring heightbeing larger toward the distal end 306 of the outer sleeve, the raisedrings 340 provide a more consistent retention force for the bolster 410(FIG. 27) along the length of the outer sleeve. The rings 340 facilitatea mechanical lock between the bolster 410 and the outer sleeve 300.Having the larger ring heights toward the distal end 306 of the sleeve300, where the diameter of the distal portion 312 of the outer sleeve issmallest, the bolster 410 relies more on the rings 340 for a surface toclamp to. Toward the proximal end 342 (FIG. 15) of the distal portion312 of the outer sleeve 300, where the diameter of the distal portion ofthe outer sleeve is largest and the ring height is smallest, the bolster410 can rely on the outer surface 322 of the distal portion of the outersleeve, as well as the rings 340, for clamping surfaces. Each of therings 340 needs to include at least one contact surface that the bolster410 may clamp against, but may include more than one contact surface.

To increase the clamp retention force between the bolster 410 (FIG. 27)and the outer sleeve 300 of the cannula assembly 210 (FIG. 13), theouter surface 322 of the outer sleeve and/or the outer surface of therings 340 may be roughened. Alternatively, the outer surface 322 of theouter sleeve 300 may be textured with dimples or raised bumps instead ofwith the rings 340. A threaded geometry may be incorporated in place ofthe concentric rings 340 with the threaded portion having a smallertaper than the outer surface 322 of the outer sleeve 300 such that thedepth of the thread is larger toward the distal end 306 of the distalportion 312 of the outer sleeve 300 and smaller toward the proximal end342 (FIG. 15) of the distal portion of the outer sleeve. Longitudinalribs may be utilized in place of the raised rings 340 with thelongitudinal ribs having a smaller taper than the outer surface 322 ofthe outer sleeve 300 such that the height of the longitudinal ribs islarger toward the distal end 306 of the distal portion 312 of the outersleeve and smaller toward the proximal end 342 of the distal portion ofthe outer sleeve.

Referring to FIG. 29, an inner surface 330 of the outer sleeve 300 mayinclude a plurality of channels 332 extending along the length of theouter sleeve from substantially the proximal end 342 (see FIG. 15) ofthe distal portion 312 of the outer sleeve distally to the distal end306 of the outer sleeve. The channels 332 are similar to the channels268 described for the outer surface of the cannula 250. The plurality ofchannels 332 on the inner surface 330 of the outer sleeve 300 is adaptedto facilitate the flow of gasses or fluids therethrough. In oneembodiment, the plurality of channels 332 on the inner surface 330 ofthe outer sleeve 300 may include a plurality of substantiallylongitudinal grooves 334 that are substantially parallel to thelongitudinal axis 320 of the outer sleeve. With the plurality ofchannels 332 on the inner surface 330 of the sleeve 300, the sleeve 300may be used with either the cannula 250 having a plurality of channels268 on the outer surface of the cannula to further increase the flow ofgasses or fluids between the sleeve and cannula, or a cannula having asubstantially smooth outer surface.

Referring again to FIGS. 13 and 26, to facilitate sealing the balloon400 (FIG. 19) around the incision in the body wall, the bolster 410includes a substantially annular pad 530 coupled to the distal surface430 of the proximal flange 424 portion of the base 420 and around theouter surface 440 of the sleeve 422 (see FIG. 23) portion of the base.In one aspect, the pad 530 is made of a substantially incompressiblegel. Since the pad 530 is substantially incompressible, it does not needto be as thick as the foam pads 180 of the prior art. Having a thinnerpad provides the cannula assembly 210 with more usable length. The pad530 may operate as a backup seal for the incision to help protectagainst leaks that might develop between the balloon and the innersurface of the body wall. In one aspect, the pad 530 may be betweenabout 3.0-20.0 mm thick. However, in another aspect the pad 530 may bethicker to promote the sealing features of the pad.

As stated above, the pad 530 may be made of gel. The pad 530 made of gelmay be attached to, formed or integrated with the base 420. In oneaspect, the gel is an elastomeric gel. In one aspect, the gel can beprepared by mixing a triblock copolymer with a solvent for themidblocks. The endblocks are typically thermoplastic materials such asstyrene and the midblocks are thermoset elastomers such as isoprene orbutadiene, e.g., Styrene-Ethylene-Butylene-Styrene (SEBS). In oneaspect, the solvent used is mineral oil. Upon heating this mixture orslurry, the midblocks are dissolved into the mineral oil and a networkof the insoluble endblocks forms. The resulting network has enhancedelastomeric properties over the parent copolymer. In one aspect, thetriblock copolymer used is KRATON G1651. Once formed, the gel issubstantially permanent and by the nature of the endblocks processableas thermoplastic elastomers henceforward. The mixture or slurry has aminimum temperature at which it becomes a gel, i.e., the minimum gellingtemperature (MGT). This temperature in one aspect corresponds to theglass transition temperature of the thermoplastic endblock plus a fewdegrees. For example, the MGT for the mixture of KRATON G1651 andmineral oil is about 120° C. When the slurry reaches the MGT and thetransformation to a gel state takes place, the gel becomes moretransparent, thereby providing a means for visually confirming when thetransformation of the slurry to the gel state is substantially completeand that the gel may be cooled. In addition to triblocks, there are alsodiblock versions of the materials that may be used where Styrene ispresent at only one end of the formula, for example,Styrene-Ethylene/Butylene (SEB).

For a given mass of slurry to form into a complete gel, the entire massof the slurry is heated to the MGT and remains heated at the MGT forsufficient time for the end blocks to form a matrix of interconnections.The slurry will continue to form into gel at temperatures above the MGTuntil the slurry/gel reaches temperatures at which the components withinthe slurry/gel begin to decompose or oxidize. For example, when theslurry/gel is heated at temperatures above 250° C., the mineral oil inthe slurry/gel will begin to be volatile and oxidize. Oxidizing maycause the gel to turn brown and become oily.

The speed at which a given volume of slurry forms a gel is dependant onthe speed with which the entire mass of slurry reaches the MGT. Also,with the application of temperatures higher than the MGT, this speed isfurther enhanced as the end block networks will distribute and form morerapidly.

The various base formulas may also be alloyed with one another toachieve a variety of intermediate properties. For example, KRATON G1701Xis a 70% SEB 30% SEBS mixture with an overall Styrene to rubber ratio of28/72. It can be appreciated that an almost infinite number ofcombinations, alloys, and Styrene to rubber ratios can be formulated,each capable of providing advantages to a particular embodiment of theinvention. These advantages will typically include low durometer, highelongation, and good tear strength.

It is contemplated that the gel material may also include silicone, softurethanes and even harder plastics with the addition of a foaming agentthat provide the desired qualities for the bolster to assist the balloon400 to seal against the inner surface of the body wall 52. The siliconematerial may be of the types currently used for electronicencapsulation. The harder plastics may include PVC, Isoprene, KRATONneat, and other KRATON/oil mixtures. In the KRATON/oil mixture, oilssuch as vegetable oils, petroleum oils and silicone oils may besubstituted for the mineral oil.

Any of the gel materials contemplated could be modified to achievedifferent properties such as enhanced lubricity, appearance, and woundprotection. Additives may be incorporated directly into the gel orapplied as a surface treatment. Other compounds may be added to the gelto modify its physical properties or to assist in subsequentmodification of the surface by providing bonding sites or a surfacecharge Additionally, oil based colorants may be added to the slurry tocreate gels of different colors.

In one aspect, the mixture/slurry used with the various embodiments ofthe bases 420 that are described herein are composed of 90% by weight ofmineral oil and 10% by weight of KRATON G1651. From a thermodynamicstandpoint, this mixture behaves similar to mineral oil. Mineral oil hasa considerable heat capacity and therefore at about 130° C. it can take3 or 4 hours to heat a pound of the slurry sufficiently to form ahomogeneous gel. Once formed, the gel can be cooled as quickly aspractical with no apparent deleterious effects on the gel. This cooling,in one aspect, is accomplished with cold-water immersion. In anotheraspect the gel may be air-cooled. Those with ordinary skill in the artwill recognize that other cooling techniques that are well know in theart may be employed and are contemplated as within the scope of thepresent invention.

Many of the properties of the KRATONI/oil mixture will vary withadjustments in the weight ratio of the components. In general, thegreater the percentage of mineral oil, the less firm the mixture; thegreater the percentage of KRATON, the more firm the mixture.

If the slurry is permitted to sit for a prolonged period of time, thecopolymer, such as KRATON, and the solvent, such as mineral oil, mayseparate. The slurry may be mixed, such as with high shear blades, tomake the slurry more homogeneous However, mixing the slurry mayintroduce or add air to the slurry. To remove air from the slurry, theslurry may be degassed. In one aspect, the slurry may be degassed in avacuum, such as within a vacuum chamber. In one aspect, the appliedvacuum may be 0.79 meters (29.9 inches) of mercury, or about 1.0atmosphere. The slurry may be stirred while the slurry is under vacuumto facilitate removal of the air. During degassing within a vacuum, theslurry typically expands, then bubbles, and then reduces in volume. Thevacuum may be discontinued when the bubbling substantially ceases.Degassing the slurry in a vacuum chamber reduces the volume of theslurry by about 10%. Degassing the slurry helps reduce the potential ofthe finished gel to oxidize.

Degassing the slurry tends to make the resultant gel firmer. A degassedslurry composed of about 91.6% by weight of mineral oil and 8.4% byweight of KRATON G1651, an eleven-to-one ratio, results in a gel havingabout the same firmness as a gel made from a slurry that is not degassedcomposed of 90% by weight of mineral oil and 10% by weight of KRATONG1651, a nine-to-one ratio.

The gel in various aspects of the present invention may be gammasterilized. As such, the relative or comparative simplicity ofqualifying the sterilization process, for example of gamma versusethylene oxide, of the gel and the device with the gel is desirable.However, under gamma sterilization large bubbles can form in the gelcausing potential cosmetic or aesthetic issues in the sterilizeddevices. The bubbles are more than 99% room air and as such removal ofthe dissolved air in the slurry prior to forming the slurry into gel isperformed. For example, the slurry may be degassed via vacuum asdescribed above and turned into gel by heat. Bubbles may still form inthe gel during gamma sterilization but disappear in a period of about 24to 72 hours. In one aspect, the percentage of dissolved gas in themineral oil at room temperature is about 10%. The removal of the air inthe gel has an additional effect of making the gel firmer. This howeveris counterbalanced by the softening effect of gamma radiation on the gelduring gamma sterilization.

In one aspect, if the gel is to be gamma sterilized, the gel may includeabout 90% mineral oil by weight and about 10% KRATON by weight. Asstated above, degassing the slurry has the effect of making the gelfirmer, however, the gamma radiation softens the gel to substantiallythe same firmness as a gel having about 90% mineral oil by weight andabout 10% KRATON by weight that is not degassed or gamma sterilized.

In one aspect, cyanoacrylate, e.g., SUPERGLUE or KRAZY GLUE, may be usedto bond or otherwise attach the pad 530 made of gel to the base 420. Theglue may attach to either the rubber or styrene component of thetri-block and the bond is frequently stronger than the gel materialitself.

In another aspect, a solvent is used to dissolve the plastics in thebase 420 and the polystyrene in the gel. The solution of solvent isapplied to the gel and base 420 in either a spray or dip form. In effectthe solution melts both the plastic of the base as well as thepolystyrene in the gel to allow a chemical bond to form between the two,which remains when the solvent evaporates.

Polyethylene can be dissolved in mineral oil and then applied to thegel. The mineral oil will not evaporate but will over time absorb intothe gel and impart a polyethylene layer on the gel that may havebeneficial properties.

In one aspect, the gel is cast into a mold containing the base 420.Adhesion between the pad 530 made of gel and the base 420 can beachieved by using KRATON polymer or a similar material in the base. Thepolystyrene in the gel is identified as achieving adhesion withpolyphenylene oxide (PPO), polystyrene and others.

In the casting process, the pad 530 made of gel and the base 420 areheated to a temperature above about 130° C. and held at that temperaturefor several hours, e.g., about 3 to 4 hours. The temperature used is notsufficient to deform the base 420.

In one aspect, the base 420 includes a polymer, e.g., polyethylene (PE).In one aspect, the polyethylene is a low-density polyethylene (LDPE) orhigh-density polyethylene (HDPE), or ultra high molecular weightpolyethylene (UHMWPE). In one aspect, the base 420 may be made of apolymer, such as polycarbonate and may be fabricated by methodsincluding injection molding.

The gel includes mineral oil. PE has a higher molecular weight thanmineral oil. PE is dissolved by mineral oil at high temperatures. Assuch, as the PE and mineral oil in the gel intermix as both are heatedto and held at temperatures above about 130° C., a bond between the PEand gel is formed.

As stated above, the base 420 may be made of polycarbonate. Thepolycarbonate of the base does not form bonds with gel at 130° C.However during casting, by raising the temperature to about 150° C. fora few minutes, bonding occurs between the pad 530 and the base. As such,heating the gel and base to temperatures at which both the polystyreneof the gel and the polycarbonate are simultaneously beyond their meltpoints allows bonds to form between the pad 530 made of gel and the base420. Alternatively, the gel and base may be heated to near or at theglass transition temperature of the polycarbonate base 420 to form thebond between the pad 530 made of gel and the base.

In one aspect, casting the pad 530 made of gel with the base 420 to formthe bolster 410 includes placing the base into a casting mold. The moldmay be made of aluminum, copper, brass, or other mold material havinggood heat dissipation properties. However, those with ordinary skill inthe art will recognize that other mold materials having lower heatdissipation properties will produce acceptable parts and these arecontemplated as within the scope of the present invention.

The mold having the base 420 is filled with the slurry. To facilitatefilling voids in the mold with the slurry, the slurry may be preheated,for example, to about 52° C. (125° F.). Preheating the slurry to atemperature below the MGT reduces the viscosity of the slurry and allowsthe slurry to flow more easily. As stated above, the slurry may havebeen degassed in a vacuum. The slurry may be degassed again within themold after the mold is filled to remove air that may have beenintroduced during the filling of the mold and to facilitate flow of theslurry into voids in the mold. Heat is applied to the mold having thebase 420 and the slurry, such as in an oven, until the slurry attains atemperature of about 150° C. As stated above, the slurry turns into gelat about 120° C., however, at about 150° C., the gel can bond to apolycarbonate base 420. Depending on the material used to fabricate thebase 420, bonding may take place at temperatures other than about 150°C. If the base 420 is fabricated of a material having a lower meltingpoint than 120° C., then the pad 530 made of gel may be moldedseparately and then bonded to the base 420.

Once the temperature of the gel reaches about 150° C., the bolster 410may be cooled, such as by air-cooling, cold-water immersion, or othercooling means that are well known in the art. At 150° C. the gel is softand if it were distorted during cooling it would set with the distortionincluded. To reduce the likelihood of distorting the pad 530 made ofgel, the bolster 410 may be cooled within the mold. Cooling times mayvary based on parameters including size and configuration of the mold,quantity of gel, temperature and quantity of cooling medium, coolingmedium properties and the mold material. Whether cooling with air orwater, the final properties of the gel are substantially the same. Thebolster 410 is typically cooled to about ambient room temperature, butmay be cooled to lower temperatures. The bolster 410 may be removed fromthe mold at any time after the gel has set.

When removed from the mold, the gel typically has a tacky surface. Thepad 530 made of gel may be coated with a powder, such as cornstarch, tosubstantially reduce or eliminate the tackiness of the cured gel.

As stated above, in another aspect, the pad 530 made of gel may bemolded separately from the base 420 and subsequently bonded to the base.In one aspect, the pad 530 made of gel may be molded into a slug. Sincethe gel 530 is being molded separate from the base 420, the slurry onlyneeds to be heated until it reaches about 120° C. and completes thetransformation from slurry into gel and the gel becomes substantiallytransparent. The pad 530 may then be placed onto the base 420. The pad530 and base 420 are heated to a sufficient temperature for thepolystyrene of the gel and the polymer of the base 420 to form bondsbetween the pad 530 and the base. Molding the pad 530 made of gelseparately from the base 420 and heat bonding the pad to the base at alater time is especially useful when the base is made of a material thathas a lower melting temperature than the MGT. In such situations, thepad 530 can be molded first and heat bonded to the base 420 withoutmelting the base.

Referring again to FIGS. 13 and 26, to facilitate sealing the balloon400 (FIG. 19) around the incision in the body wall, the bolster 410includes a pad 530 coupled to the base 420 around the outer surface 440of the sleeve 422 (see FIG. 23) portion of the base. In one aspect, thepad 530 is substantially annular. In one aspect, the pad 530 is made ofan elastomeric, polymeric material, such as silicone. Since silicone isnot as compliant as the gel described above, the pad 530 may be a pad600 including a hollow portion 620 (FIGS. 33 and 35) to providecompliancy. The hollow pad 600 may operate as a backup seal for theincision to help protect against leaks that might develop between theballoon and the inner surface of the body wall.

Referring to FIGS. 32-36, the pad 600 includes a hollow body 602 havinga longitudinal axis 604. In one aspect, the hollow body 602 issubstantially cylindrical. Being substantially hollow, the body 602includes a peripheral wall 606 having a thickness. Those with ordinaryskill in the art will recognize that the pad may include shapes otherthan cylindrical. The hollow pad 600 includes a proximal, retentionflange 608 and a distal, body contact flange 610. The retention flange608 is positioned at the proximal end of the pad 600 and extendsradially inwardly from the wall 606. The retention flange 608 includesan aperture 612 that is positioned along the axis 604 of the pad 600 andis sized to receive the sleeve 422 portion of the base 420. Theretention flange 608 of the pad 600 may include surface features thatinteract with the base 420 to facilitate coupling of the pad to thebase. The distal, body contact flange 610 of the pad 600 is positionedat the distal end of the pad and extends radially inwardly from the wall606 of the pad. The body contact flange 610 includes an aperture 614that is positioned along the axis 604 of the pad 600 and is sized toreceive the cannula assembly 210 (FIG. 13). In one aspect, the aperture614 of the body contact flange 610 is smaller than the perimeter of thedistal portion 312 of the sleeve 300 portion of the cannula assembly 210so as to provide a seal between the hollow pad 600 and the sleeveportion of the cannula assembly (FIG. 36). A proximally-facing lip 616may extend from the perimeter of the aperture 614 in the body contactflange 610. A plurality of gussets 618 may be positioned around the lip616, extending radially outwardly therefrom, and couple the lip to thewall 606 of the pad 600 to substantially prevent inversion of the lip asthe bolster 410 moves along the length of the cannula assembly 210 (FIG.13). The lip 616 geometry, combined with the gussets 618, providestructural strength to the pad 600, substantially preventing the pad 600from turning inside-out when under a load. The wall 606 forms acompliant, compression portion 620 of the pad 600. The wall 606 isflexible and has shape memory, thereby allowing the wall to act as aspring to facilitate maintaining the balloon 400 against the innersurface 54 of the abdominal wall 50 of the patient. In one aspect, thewall 606 of the hollow pad 600 also facilitates sealing between the bodycontact flange 610 and the skin of the patient.

The base 420 includes a second, distal, pad retaining flange 458positioned along the sleeve 422 distal the first, proximal flange 424.The distal, pad retaining flange 458 is substantially annular, but thosewith ordinary skill in the art will recognize that the pad retainingflange may include other shapes. The pad retaining flange 458 mayinclude surface features to facilitate retention of the pad 600. Thedistal, pad retaining flange 458 and the proximal flange 424 are spacedso as to retain the retention flange 608 of the pad 600 when positionedtherebetween. The perimeter of the distal, pad retaining flange 458 ofthe base 420 is less than or equal to the perimeter of the inner surface622 of the pad 600.

As stated above, the pad 600 may be made of silicone. The durometer ofthe material of which the pad 600 is made, such as silicone, combinedwith the geometry of the pad, provide the pad 600 with shape memory. Thehollow pad 600 acts like a spring and is deformable to substantiallymatch the contours of the body tissue when the bolster 410 is moved intocontact with the body tissue. The pad 600 may be made through the use ofliquid injection molding; however, those with ordinary skill in the artwill recognize other well known methods for making the pad. The pad 600may be made of materials other than silicone, including KRATON(Styrene-Ethylene-Butylene-Styrene (SEBS)), KRATON combined with afoaming agent, and other elastomeric materials that are well known inthe art. The finished pad 600 may be coupled to the base 420 bystretching the retention flange 608 of the pad over the pad retainingflange 458 of the base 420, and letting the retaining flange of the padsnap into the space between the distal, pad retaining flange of the baseand the proximal flange 424 of the base. The material of which the pad600 is made is not sufficiently compliant to permit the retention flange608 of the pad to be easily pulled back over the distal, pad retainingflange 458 of the base 420 during its intended use. In one aspect, thepad 600 may be coupled to the base 420 through other means, includingbonding, molding the pad directly to the base, and other means that arewell known in the art. The pad 600 may also include other hollowconfigurations that are well known in the art for providing thecompression portion 620 of the pad.

During a surgical procedure in which the balloon trocar 200 of thepresent invention may be used, a surgeon may gain access to theabdominal cavity 52 through the abdominal wall 50 by using the “Hassan”or “cut-down” technique. However, use of the Hassan or cut-downtechnique often leaves a defect larger than the trocar that will belocated through the incision. Therefore, it is necessary to provide ameans to seal the incision after the trocar has been inserted in orderto insufflate the patient's abdominal cavity. The balloon trocar 200 ofthe present invention provides such sealing means.

Referring to FIG. 17, once an incision is made in the body wall 50 togain entry to the body cavity 52, such as the abdominal cavity, thedistal end of the balloon trocar 200 is inserted through the incisionuntil the balloon 400 at the distal portion of the cannula assembly 210is within the body cavity. A syringe 540 may be inserted into the port380 and used to inflate the balloon 400 by injecting gas or fluid intothe chamber 408. To seal the balloon 400 against the interior surface ofthe body wall 50, the bolster 410 may be advanced distally along thecannula while pulling the balloon trocar 200 proximally until theinflated balloon is compressed against the inner surface of the bodywall 50 and the pad 530, 600 is compressed against the outer surface ofthe body wall The lever 500 may be rotated to apply clamping force fromthe clamp mechanism 415 onto the outer sleeve 300 to maintain theposition of the bolster on the cannula assembly 210, thereby maintainingcompression of the balloon 400 against the interior surface of the bodywall 50 and compression of the pad 530, 600 against the exterior surfaceof the body wall. With the incision sealed, the body cavity 52, such asthe abdominal cavity, may be insufflated with CO₂ or a similar gas. Todeflate the balloon 400 for removal of the balloon trocar 200 from thebody cavity 52, the plunger 384 (see FIG. 18) within the port 380 may bedepressed to release the gas or fluid from the balloon. The syringe 540may be used to depress the plunger 384 within the port 380 and thesyringe used to pull the gas or fluid from the chamber 408, therebydeflating the balloon 400.

It will be understood that many other modifications can be made to thevarious disclosed embodiments without departing from the spirit andscope of the concept. For example, various sizes of the surgical deviceare contemplated as well as various types of constructions andmaterials. It will also be apparent that many modifications can be madeto the configuration of parts as well as their interaction. For thesereasons, the above description should not be construed as limiting theinvention, but should be interpreted as merely exemplary of manyembodiments. Those with ordinary skill in the art will envision othermodifications within the scope and spirit of the present invention asdefined by the following claims.

1. A cannula assembly, comprising: a cannula including a substantially longitudinal tube having a proximal end, a distal end, a lumen extending between the proximal end and the distal end, a proximal portion having a first, larger periphery, a distal portion having a second, smaller periphery, an annular groove on the outer surface of the distal portion of the cannula toward the distal end of the cannula, and a plurality of channels on the outer surface of the distal portion of the cannula, the plurality of channels extending along the length of the cannula from substantially a proximal end of the distal portion of the cannula distally to a point proximal to the annular groove near the distal end of the cannula; a sleeve including a substantially longitudinal tube having a proximal end, a distal end, a lumen extending between the proximal end and the distal end, a proximal portion having a first, larger periphery, a distal portion having a second, smaller periphery, and an annular groove on the outer surface of the distal portion of the sleeve toward the distal end of the sleeve, the lumen of the sleeve being configured to accept the cannula; a balloon including a tubular sleeve, the balloon being coupled to the annular groove on the outer surface of the distal portion of the sleeve, extending distally from the distal end of the sleeve to the annular groove on the outer surface of the distal portion of the cannula, and being coupled to the annular groove of the cannula; grease, the grease coating an inner surface of the balloon; and a seal positioned between the cannula and the sleeve and compressed sufficiently to form a seal between the cannula and the sleeve, wherein the sleeve being coupled to the cannula and positioned over the cannula with the proximal portion of the sleeve fitting over at least a distal region of the proximal portion of the cannula and the distal portion of the sleeve fitting over at least a portion of the distal portion of the cannula, the distal end of the sleeve being positioned proximal to the distal ends of the plurality of channels on the outer surface of the cannula, and the space between the outer surface of the cannula with the plurality of channels, the inner surface of the sleeve, the seal, and the balloon forming a substantially closed chamber.
 2. The cannula assembly of claim 1, wherein the plurality of channels on the outer surface of the cannula includes a plurality of substantially longitudinal grooves that are substantially parallel to a longitudinal axis of the cannula.
 3. The cannula assembly of claim 1, further comprising: an obturator adapted to be removably positioned within the lumen of the cannula, the obturator comprising, an elongate shaft extending along a substantially longitudinal axis between a proximal end and a distal end, and a distal tip having a prolate spheroid shape.
 4. The cannula assembly of claim 1, further comprising: a trocar seal positioned at the proximal portion of the cannula, the trocar seal including a valve that provides an instrument seal in the presence of an instrument and provides a zero-seal in the absence of an instrument.
 5. The cannula assembly of claim 1, the inner surface of the distal portion of the sleeve including a plurality of channels extending along the length of the sleeve from substantially a proximal end of the distal portion of the sleeve distally to the distal end of the sleeve.
 6. The cannula assembly of claim 5, wherein the plurality of channels on the inner surface of the sleeve includes a plurality of substantially longitudinal grooves, wherein each of the longitudinal groove is substantially parallel to a longitudinal axis of the sleeve.
 7. The cannula assembly of claim 1, the grease including silicone grease.
 8. The cannula assembly of claim 1, the tubular sleeve of the balloon including a silicone tubular sleeve and the grease including silicone grease.
 9. A cannula assembly, comprising: a cannula including a substantially longitudinal tube having a proximal end, a distal end, a lumen extending between the proximal end and the distal end, an outer surface, and a plurality of channels on the outer surface of the cannula, the plurality of channels extending along the length of the cannula from a proximal end adjacent the proximal end of the cannula to a distal end adjacent the distal end of the cannula; a sleeve including a substantially longitudinal tube having a proximal end, a distal end, and a lumen extending between the proximal end and the distal end, the lumen defining an inner surface of the sleeve, and the lumen of the sleeve being configured to accept the cannula; a balloon including a tubular sleeve, the tubular sleeve including a distensible thermoplastic elastomeric material, the balloon sealingly coupled to the distal end of the sleeve, extending distally from the distal end of the sleeve, and sealingly engaged to the cannula at a location distal the distal end of the sleeve; and wherein the sleeve is coupled to the cannula and positioned over the cannula with the proximal end of the sleeve sealingly engaging the cannula adjacent the proximal end of the cannula, the distal end of the sleeve being positioned proximal to the distal ends of the plurality of channels on the outer surface of the cannula, and the space defined by the outer surface of the cannula with the plurality of channels, the inner surface of the sleeve, the seal, and the balloon forming a substantially closed chamber.
 10. The cannula assembly of claim 9, wherein the plurality of channels on the outer surface of the cannula includes a plurality of substantially longitudinal grooves that are substantially parallel to a longitudinal axis of the cannula.
 11. The cannula assembly of claim 9, further comprising: an obturator adapted to be removably positioned within the lumen of the cannula, the obturator comprising, an elongate shaft extending along a substantially longitudinal axis between a proximal end and a distal end, and a distal tip having a prolate spheroid shape.
 12. The cannula assembly of claim 9, further comprising: a trocar seal positioned at the proximal end of the cannula, the trocar seal including a valve that provides an instrument seal in the presence of an instrument and provides a zero-seal in the absence of an instrument.
 13. The cannula assembly of claim 9, the inner surface of the distal portion of the sleeve including a plurality of channels extending along the length of the sleeve.
 14. The cannula assembly of claim 13, wherein the plurality of channels on the inner surface of the sleeve includes a plurality of substantially longitudinal grooves, wherein each of the longitudinal groove is substantially parallel to a longitudinal axis of the sleeve.
 15. The cannula assembly of claim 9, the distensible thermoplastic elastomeric material of the tubular sleeve of the balloon including styrene-ethylene-butylene-styrene tri-block polymer.
 16. The cannula assembly of claim 9, further comprising grease, the grease coating an inner surface of the balloon.
 17. The cannula assembly of claim 16, the grease including silicone grease. 